In U.S. Pat. No. 4,326,557 granted Apr. 27, 1982, a top operated lading valve assembly including a threaded valve cage located inside the tank is disclosed which is installed from the bottom of the tank. Thus the attendant need not enter the tank to install or replace this lading valve assembly.
However, if the operating rod which extends to the top of the tank becomes broken or otherwise inoperative, a problem arises as to how to move the lading valve between open and closed positions. If the lading valve is closed and lading is located within the tank, an arrangement is needed to open the lading valve without the attendant having to enter a loaded tank.
In U.S. Pat. No. 4,137,937, issued Feb. 6, 1979, an adapter is disclosed for use in connection with a bottom operated tank car lading valve. This adapter is intended for use at destination to load and/or unload the lading. One embodiment includes a pair of unloading spouts to facilitate unloading in emergency situations such as unloading the lading in a derailed railway tank car.
However, this adapter is designed for use with a bottom operated tank car valve having a bottom operating mechanism which does not include a threaded cage through which top operator rotates in moving the lading valve between open and closed position. Furthermore, there is no need to move a rotatable element into threaded engagement with the remaining portion of the top operating rod to rotatably move the remaining operating rod portion of the top operating rod through the valve cage.
In U.S. Pat. No. 4,240,607, granted Dec. 23, 1980, a top operable lading valve assembly is disclosed including a valve seal retainer including a vertical projection extending through an opening in the lading valve into an opening in the bottom surface of the top operating rod. After removal of the outlet chamber if the top operating rod is damaged, the lading valve is operable from the bottom of the tank by removing the seal retainer and extending a tool having a non-round end into the non-round opening in the bottom of the remaining portion of the top operating rod, rotating the rod through the cage and lifting the lading valve to open position.
However, this arrangement is undesirable because with the outlet chamber removed if there is lading in the tank when the tool is inserted and the valve opened, there is no convenient way of attaching a pipe or container to collect the lading.